Nicotine has been proposed to have a number of pharmacological effects. See, for example, Pullan et al., N. Engl. J. Med. 330:811 (1994). Certain of those effects may be related to effects upon neurotransmitter release. See, for example, Sjak-shie et al., Brain Res. 624:295 (1993), where neuroprotective effects of nicotine are proposed. Release of acetylcholine and dopamine by neurons, upon administration of nicotine, has been reported by Rowell et al., J. Neurochem. 43:1593 (1984); Rapier et al., J. Neurochem. 50:1123 (1988); Sandor et al., Brain Res. 567:313 (1991) and Vizi, Br. J. Pharmacol. 47:765 (1973). Release of norepinephrine by neurons, upon administration of nicotine, has been reported by Hall et al., Biochem. Pharmacol. 21:1829 (1972). Release of serotonin by neurons, upon administration of nicotine, has been reported by Hery et al., Arch. Int. Pharmacodyn. Ther. 296:91 (1977). Release of glutamate by neurons, upon administration of nicotine, has been reported by Toth et al., Neurochem Res. 17:265 (1992). Confirmatory reports and additional recent studies have included the modulation, in the central nervous system (CNS), of glutamate, nitric oxide, GABA, tachykinins, cytokines, and peptides (reviewed in Brioni et al., Adv. Pharmacol. 37:153 (1997)). In addition, nicotine reportedly potentiates the pharmacological behavior of certain pharmaceutical compositions used for the treatment of certain disorders. See, for example, Sanberg et al., Pharmacol. Biochem. & Behavior 46:303 (1993); Harsing et al., J. Neurochem. 59:48 (1993) and Hughes, Proceedings from Intl. Symp. Nic. S40 (1994). Furthermore, various other beneficial pharmacological effects of nicotine have been proposed. See, for example, Decina et al., Biol. Psychiatry 28:502 (1990); Wagner et al., Pharmacopsychiatry 21:301 (1988); Pomerleau et al., Addictive Behaviors 9:265 (1984); Onaivi et al., Life Sci. 54 (3):193 (1994); Tripathi et al., JPET 221:91 (1982) and Hamon, Trends in Pharmacol. Res. 15:36 (1994).
Various compounds that target nAChRs have been reported as being useful for treating a wide variety of conditions and disorders. See, for example, Williams et al., DN&P 7 (4):205 (1994); Arneric et al., CNS Drug Rev. 1 (1):1 (1995); Arneric et al., Exp. Opin. Invest. Drugs 5 (1):79 (1996); Bencherif et al., JPET 279:1413 (1996); Lippiello et al., JPET 279:1422 (1996); Damaj et al., J. Pharmacol. Exp. Ther. 291:390 (1999); Chiari et al., Anesthesiology 91:1447 (1999); Lavand'homme and Eisenbach, Anesthesiology 91:1455 (1999); Holladay et al., J. Med. Chem. 40 (28): 4169 (1997); Bannon et al., Science 279: 77 (1998); PCT WO 94/08992, PCT WO 96/31475, PCT WO 96/40682, and U.S. Pat. Nos. 5,583,140 to Bencherif et al., 5,597,919 to Dull et al., 5,604,231 to Smith et al., and 5,852,041 to Cosford et al. Nicotinic compounds are reported as being particularly useful for treating a wide variety of CNS disorders. Indeed, a wide variety of compounds have been reported to have therapeutic properties. See, for example, Bencherif and Schmitt, Current Drug Targets: CNS and Neurological Disorders 1 (4): 349 (2002), Levin and Rezvani, Current Drug Targets: CNS and Neurological Disorders 1 (4): 423 (2002), O'Neill et al., Current Drug Targets: CNS and Neurological Disorders 1 (4): 399 (2002), U.S. Pat. Nos. 5,1871,166 to Kikuchi et al., 5,672,601 to Cignarella, PCT WO 99/21834, and PCT WO 97/40049, UK Patent Application GB 2295387, and European Patent Application 297,858.
CNS disorders are a type of neurological disorder. CNS disorders can be drug induced; can be attributed to genetic predisposition, infection or trauma; or can be of unknown etiology. CNS disorders comprise neuropsychiatric disorders, neurological diseases and mental illnesses, and include neurodegenerative diseases, behavioral disorders, cognitive disorders and cognitive affective disorders. There are several CNS disorders whose clinical manifestations have been attributed to CNS dysfunction (i.e., disorders resulting from inappropriate levels of neurotransmitter release, inappropriate properties of neurotransmitter receptors, and/or inappropriate interaction between neurotransmitters and neurotransmitter receptors). Several CNS disorders can be attributed to a deficiency of choline, dopamine, norepinephrine and/or serotonin. Relatively common CNS disorders include pre-senile dementia (early-onset Alzheimer's disease), senile dementia (dementia of the Alzheimer's type), micro-infarct dementia, AIDS-related dementia, Creutzfeld-Jakob disease, Pick's disease, Parkinsonism including Parkinson's disease, Lewy body dementia, progressive supranuclear palsy, Huntington's chorea, tardive dyskinesia, hyperkinesia, mania, attention deficit disorder, anxiety, dyslexia, schizophrenia, depression, obsessive-compulsive disorders and Tourette's syndrome.
The nAChRs characteristic of the CNS have been shown to occur in several subtypes, the most common of which are the α4β2 and α7 subtypes. See, for example, Schmitt, Current Med. Chem. 7: 749 (2000). Ligands that interact with the α7 nAChR subtype have been proposed to be useful in the treatment of schizophrenia. There are a decreased number of hippocampal nAChRs in postmortem brain tissue of schizophrenic patients. Also, there is improved psychological effect in smoking versus non-smoking schizophrenic patients. Nicotine improves sensory gating deficits in animals and schizophrenics. Blockade of the α7 nAChR subtype induces a gating deficit similar to that seen in schizophrenia. See, for example, Leonard et al., Schizophrenia Bulletin 22 (3): 431 (1996). Biochemical, molecular, and genetic studies of sensory processing, in patients with the P50 auditory-evoked potential gating deficit, suggest that the α7 nAChR subtype may function in an inhibitory neuronal pathway. See, for example, Freedman et al., Biological Psychiatry 38 (1):22 (1995).
More recently, α7 nAChRs have been proposed to be mediators of angiogenesis, as described by Heeschen et al., J. Clin. Invest. 100: 527 (2002). In these studies, inhibition of the α7 subtype was shown to decrease inflammatory angiogenesis. Also, α7 nAChRs have been proposed as targets for controlling neurogenesis and tumor growth (Utsugisawa et al., Molecular Brain Research 106 (1-2): 88 (2002) and U.S. Patent Application 2002/0016371). Finally, the role of the α7 subtype in cognition (Levin and Rezvani, Current Drug Targets: CNS and Neurological Disorders 1 (4): 423 (2002)), neuroprotection (O'Neill et al., Current Drug Targets: CNS and Neurological Disorders 1 (4): 399 (2002) and Jeyarasasingam et al., Neuroscience 109 (2): 275 (2002)), and neuropathic pain (Xiao et al., Proc. Nat. Acad. Sci. (US) 99 (12): 8360 (2002)) has recently been recognized.
Various compounds have been reported to interact with α7 nAChRs and have been proposed as therapies on that basis. See, for instance, PCT WO 99/62505, PCT WO 99/03859, PCT WO 97/30998, PCT WO 01/36417, PCT WO 02/15662, PCT WO 02/16355, PCT WO 02/16356, PCT WO 02/16357, PCT WO 02/16358, PCT WO 02/17358, Stevens et al., Psychopharm. 136: 320 (1998), Dolle et al., J. Labelled Comp. Radiopharm. 44: 785 (2001) and Macor et al., Bioorg. Med. Chem. Lett. 11: 319 (2001) and references therein. Among these compounds, a common structural theme is that of the substituted tertiary bicylic amine (e.g., quinuclidine). Similar substituted quinuclidine compounds have also been reported to bind at muscarinic receptors. See, for instance, U.S. Pat. No. 5,712,270 to Sabb and PCTs WO 02/00652 and WO 02/051841.
It would be desirable to provide a useful method for the prevention and treatment of a condition or disorder by administering a nicotinic compound to a patient susceptible to or suffering from such a condition or disorder. It would be highly beneficial to provide individuals suffering from certain disorders (e.g., CNS diseases) with interruption of the symptoms of those disorders by the administration of a pharmaceutical composition containing an active ingredient having nicotinic pharmacology which has a beneficial effect (e.g., upon the functioning of the CNS), but does not provide any significant associated side effects. It would be highly desirable to provide a pharmaceutical composition incorporating a compound that interacts with nAChRs, such as those that have the potential to affect the functioning of the CNS. It would be highly desirable that such a compound, when employed in an amount sufficient to affect the functioning of the CNS, would not significantly affect those nAChR subtypes that have the potential to induce undesirable side effects (e.g., appreciable activity at cardiovascular and skeletal muscle receptor sites). In addition, it would be highly desirable to provide a pharmaceutical composition incorporating a compound which interacts with nicotinic receptors but not muscarinic receptors, as the latter are associated with side effects, such as hypersalivation, sweating, tremors, cardiovascular and gastrointestinal disturbances, related to the function of the parasympathetic nervous system (see Caulfield, Pharmacol. Ther. 58: 319 (1993) and Broadley and Kelly, Molecules 6: 142 (2001)). Furthermore, it would be highly desirable to provide pharmaceutical compositions, which are selective for the α7 nAChR subtype, for the treatment of certain conditions or disorders (e.g., schizophrenia, cognitive disorders, and neuropathic pain) and for the prevention of tissue damage and the hastening of healing (i.e., for neuroprotection and the control of angiogenesis). The present invention provides such compounds, compositions and methods.